WO2006016102A1

WO2006016102A1 - Downhole cleaning apparatus

Info

Publication number: WO2006016102A1
Application number: PCT/GB2005/002914
Authority: WO
Inventors: Joseph Fitzgerald; Alan Martyn Eddison
Original assignee: Andergauge Limited
Priority date: 2004-08-10
Filing date: 2005-07-26
Publication date: 2006-02-16
Also published as: GB0417732D0

Abstract

Downhole cleaning apparatus in the form of a casing scraper (10) comprises body (12) and cleaning members (22) mounted on the body. The cleaning members (22) are selectively movable from a retracted configuration to an extended cleaning configuration. The casing scraper (10) may be mounted on a drill string above a drill bit.

Description

DOWNHOLE CLEANING APPARATUS

FIELD OF THE INVENTION This invention relates to a downhole apparatus, and in particular, but not exclusively, to a downhole cleaning apparatus, such as a casing scraper tool. The invention also relates to a downhole cleaning method.

BACKGROUND OF THE INVENTION In the oil and gas exploration and production industry, subsurface hydrocarbon-bearing formations are accessed by drilling bores from surface. The bores are lined with metal tubing, known as casing and liner, with the annular space between the tubing and the bore wall being sealed with cement. Casing is generally suspended from surface level, whereas the first section of liner is generally hung from the lower end of the last casing section. The liner is coupled to the casing by an arrangement known as a liner hanger, which engages the inner surface of the casing. In order to achieve a reliable grip and a pressure-tight seal between the hanger and the casing it is important that the surface of the casing is relatively clean and smooth. The cleaning of the casing is typically achieved using a tool known as a casing scraper, as described below.

After a casing section has been cemented in a bore, there will normally be a plug of set cement left at the bottom of the bore, within and beyond the end of the casing. The end of the casing will also normally feature a casing shoe, formed of a soft or frangible material, which may have served to facilitate running the casing into the bore and feature cement flow control valves. To drill the bore beyond the end of the casing it is therefore first necessary to drill through the cement plug and the shoe, and then drill the bore beyond the end of the casing to the necessary depth, ready to accommodate the next section of casing or liner. When liner is to be hung from the last section of casing, after the bore has been drilled to the required depth and the drill string pulled out of the hole, a casing scraper is run into the bore to clean the area of the casing which will accommodate the liner hanger. A conventional casing scraper comprises a plurality of sprung scraping blades biased to describe a diameter slightly larger than the inner diameter of the casing to be cleaned. Thus, once the scraper is located in the appropriate section of casing, reciprocating the tool scrapes the blades across the casing surface, dislodging any material which would otherwise interfere with the subsequent location of the liner hanger.

Once the casing scraper has been pulled out of the bore, the liner hanger is run into the cleaned casing and set.

SUMMARY OF THE INVENTION

According to the present invention there is provided a downhole cleaning apparatus comprising: a body; and at least one cleaning member mounted on the body, the cleaning member being selectively movable from a retracted position to an extended cleaning position.

The ability to retain the cleaning member in a retracted position allows the apparatus to, for example, be mounted on a drill string above a drill bit, such that following a drilling operation the cleaning member may be moved to the extended position and utilised in a cleaning operation, for example to clean a section of casing wall ready to receive a liner hanger. This contrasts with conventional casing scrapers which have scraper blades normally configured to engage with the inner surface of the casing to be cleaned. Clearly, if such a casing scraper were mounted on a drill string, during the drilling operation the scraper blades would be rotated with the drill string, all the while being urged into contact with the bore wall. This would lead very quickly to the destruction of the blades and, if the casing scraper was located within the casing at that point, would cause significant damage to the casing.

Also, as the cleaning member may only be moved to the extended position immediately prior to cleaning being required, the cleaning member will not have experienced the wear and potential damage that a conventional scraper is subject to as it is run in through a bore to a cleaning location.

In accordance with another aspect of the present invention there is provided a method of cleaning downhole tubing, the method comprising: mounting a cleaning apparatus on a drill string above a drill bit; and reconfiguring a cleaning member on the cleaning apparatus to a cleaning configuration.

Preferably, the cleaning member includes a compliant element. Typically, an outer portion of the cleaning member will be radially compliant, and in an extended or cleaning configuration will be biased radially outwardly to define a diameter larger than the inner diameter of a bore surface to be cleaned. This allows for more effective cleaning of the bore wall, and also facilitates withdrawal of the apparatus from the bore without the requirement to retract the cleaning member. hi a preferred embodiment, the outer portion of the cleaning member is initially fixed or restrained relative to an inner portion of the cleaning member, or the body. The outer portion of the cleaning member may be spring-mounted, and on release may move radially outwards under the influence of the spring. Thus, merely by releasing the outer portion, the cleaning member is at least partially extended, obviating or minimising the requirement to provide means for physically moving the cleaning member to the cleaning position. The initial location of the inner and outer portions is also preferably such that there is no cavity between the portions which could fill with material and subsequently prevent or restrict relative movement of the portions.

The cleaning member may include teeth or blades. Preferably, the teeth are inclined to facilitate scraping of the bore wall surface as the apparatus is rotated or reciprocated.

Preferably, the cleaning member is positively retained in the retracted position. Thus, centrifugal force created by the rotation of the apparatus, if incorporated in a drill string, will not extended the cleaning member prematurely. The cleaning member may be retained by any appropriate means, such as shear members, for example shear pins extending between the cleaning member and the body. Alternatively or in addition, the cleaning member may positively engage an actuating member. In a preferred embodiment the cleaning member and an actuating member are coupled via a dovetail arrangement. Preferably, the cleaning member is actuated by fluid pressure. The fluid pressure may act directly on the cleaning member but preferably acts indirectly on the cleaning member via an actuating arrangement or member. The actuating member may include a cam arranged to produce radial movement of the cleaning member in response to axial movement of the actuating member. The cam member may positively engage the cleaning member such that the radial movement of the cleaning member is prevented or restricted in the absence of axial movement of the cam member. The radial extension of the cleaning member may be achieved by rotation or pivoting of the member relative to the body but is most preferably achieved by linear radial translation of the cleaning member. Preferably, the positive engagement between the cam member and the cleaning member is provided by cooperating linearly extending profiles, which also serve to ensure that there is little if any rotation of the cleaning member relative to the body.

The actuating member may be adapted to create a fluid pressure differential thereacross. The pressure differential may be between the interior of the apparatus and the exterior of the apparatus but is preferably between an upper and lower portion of a throughbore defined by the member. The actuating member may define a flow restriction adapted to create an actuating pressure force thereacross, but most preferably is adapted to engage with a flow restricting member, such as a ball or dart, which can be selectively located in the actuating member to allow creation of an actuating pressure force across the flow restricting member sufficient to extend the cleaning member. This permits, for example, a ball to be dropped into a drill string incorporating the cleaning apparatus when it is desired to actuate the apparatus. The flow-restricting member may substantially occlude the actuating member throughbore, but subsequent movement of the actuating member may open a flow path through the bore, thereby maintaining circulation of fluid through the portion of the drill string below the cleaning apparatus. In other embodiments the cleaning member or actuating member may be actuated by other means, including mechanical force.

The actuating member may be arranged to release an outer portion of the cleaning member relative to an inner portion of the cleaning member. Once released, the outer portion may be compliant or biased radially outwardly. The release of the outer portion may be achieved by the actuating member moving the outer member radially relative to the inner member and shearing or otherwise separating a coupling member between the portions. The actuating member may be biased towards a cleaning member retracting position. Thus, the cleaning member may be retracted following a cleaning operation, to facilitate removal of the apparatus from the bore, or to allow other operations to be carried out without contact between the cleaning member and the bore wall. This may be achieved by providing a spring between the actuating member and the body.

Preferably, the body includes at least one flow port which is adapted to be selectively opened to permit flow of fluid directly from the interior of the body to the exterior of the body. Thus, in use, fluid may flow directly from the drill string into the annulus between the drill string and the casing. This provides for more effective clean out of the annulus above the port, and is useful in carrying debris dislodged by the cleaning member to surface. Also, the port may be directed towards the cleaning member and thus the flow of fluid from the port may assist in dislodging debris from the casing and also in maintaining the cleaning member itself free of debris. Preferably, the flow port is adapted to be opened as the cleaning member is extended. The resulting pressure drop in the fluid being supplied to the drill string in which the cleaning apparatus is located provides a convenient indicator to the operators on surface that the cleaning member has been extended.

Preferably, the cleaning member is located in a window in the body, and seals may be provided therebetween to prevent the ingress of material between the member and the body.

The body may define an outer diameter and the retracted cleaning member may define an outer diameter the same as or less than the body outer diameter, thus protecting the retracted cleaning member as the apparatus is moved in the bore, and furthermore protecting the bore wall and tools and devices within the bore from the cleaning member.

Preferably, a plurality of circumferentially spaced cleaning members are provided.

Although reference is made primarily herein to the location of the cleaning apparatus in a drill string, for actuation following a drilling operation, it will be apparent to those of skill in the art that the apparatus may be employed in many other situations, for example, the apparatus may be the only tool mounted on a string, or may be mounted on a tool string with one or more other tools or devices. Furthermore, while primarily intended for use in downhole environments, the apparatus and method of the invention may also be utilised in other environments, such as in risers and pipelines.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the drawings will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a sectional view of downhole cleaning apparatus in accordance with a preferred embodiment of the present invention; Figure 2 is an enlarged view of area 2 of Figure 1 ;

Figure 3a is an enlarged perspective view of a cleaning member of the apparatus of Figure 1;

Figure 3b is a sectional view of the cleaning member; Figure 4 is a view of the apparatus of Figure 1; Figure 5a is a sectional view on line 5-5 of Figure 4;

Figure 5b is an enlarged view of area G of Figure 5a; Figure 6a is a sectional view on line 6-6 of Figure 4; and Figure 6b is an enlarged view of area H of Figure 6a.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is made to the Figures, which illustrate downhole cleaning apparatus, in the form of a casing scraper 10, in accordance with a preferred embodiment of the present invention.

The casing scraper 10 comprises an elongate generally cylindrical body 12 having pin and box connections 14, 15 at its ends to permit the scraper 10 to be incorporated in a drill string. The body 12 defines a throughbore 16 to permit passage of drilling fluid. Three windows 18 (only one shown) are provided in the body wall 20 and each accommodates a respective cleaning member 22, a seal 23 mounted on each cleaning member 22 preventing ingress of material between the member 22 and the body 12. The windows 18 are formed in raised ribs in the body, the flutes between the ribs facilitating fluid passage between the scraper and the surrounding bore wall. The body also accommodates an actuating member 24 which is adapted to move the cleaning members 22 from a retracted position (as illustrated the Figures), in which the members 22 lie within the outer diameter of the body 12, to an extended cleaning position in which the members 22 will contact the inner surface of casing to be cleaned. Each cleaning member 22 comprises two main elements, an inner portion 26 which positively engages a cam portion 28 of the actuating member 24 and, in the retracted position, extends into the body, and an outer portion 30 featuring inclined cleaning blades 32. As will be noted from Figure 3, the blades 32 on each member 22 are in two sections, divided by an axially extending channel 37. The blades 32 are inclined to the horizontal, such that downward movement of the blades relative to a casing will tend to direct debris removed from the casing towards the channel 37. It will also be noted that the blades 32 describe an arc, such that they will conform to the surface of the casing to be cleaned. The inner and outer portions 26, 30 are initially fixed relative to one another by shear pins 33, but once actuated, as will be described, a degree of relative radial movement is permitted, with the outer portion 30 being urged radially outwards by springs 35. The outwards movement of the outer portion 30 is restrained by pins 34 (Figure 6) which extend through the outer portion 30 to engage the inner portion 26.

The actuating member 24 extends axially through a central portion of the body 12, and defines a throughbore 36. The member 24 is initially restrained relative to the body 12 by shear pins 38 (Figure 1) and thus, by virtue of the positive engagement with the cleaning members 22, via a dovetail slot arrangement 40, the cleaning members 22 are positively retained in the retracted position. The cleaning members 22 engage the cam portion 28 of the actuating member 24, which portion 28 includes an inclined, dovetailed, cam face. The leading end of the cam portion 28 includes a more steeply inclined face which initially engages the inner end of a rod 42 which extends from the cleaning member outer portion 30, through the inner portion 26. On initial movement of the actuating member 24, the engagement between the rod 42 and the cam portion 28 causes the outer portion 30 to be pushed outwardly more quickly than the inner portion 26, thus shearing the pin 33 which initially fixes the portions

26, 30 together. The lower end of the actuating member 24 includes a ball catcher 44; when it is desired to actuate the scraper 10, a ball 46 is dropped from surface, through the drill string, and lands on the catcher 44. With the drilling fluid pumps operating, the occlusion of the string throughbore by the ball 46 creates a significant differential pressure across the actuating member 24, which will shear the pins 38 and thus allow the actuating member to move axially downwards relative to the body 12. This movement has a number of consequences, most significantly the extension of the cleaning members 22 to a cleaning position extending beyond the outer circumference of the body 12, and the shearing of the pin 33 fixing the cleaning member inner and outer portions 26, 30.

The movement of the actuating member 24 also opens a flow passage between the actuating member throughbore 36 and jetting nozzles 48 associated with each cleaning member 22, by locating actuating member flow ports 50 within a chamber 52 in communication with the nozzles 48. This provides a jet of fluid directed towards each cleaning member 22, the fluid assisting in dislodging debris from the casing and carrying debris away from the cleaning location. As is perhaps most clearly evident from Figure 4, each nozzle 48 is directed towards and aligned with the associated cleaning member channel 37, thus inducing flow in the channel 37 and causing debris to be drawn into the channel 35 from the troughs between the adjacent blades 32. Also, the opening of the nozzles allows a relatively high flow rate to be achieved, and thus assists in carrying debris to surface.

Downward movement of the actuating member 24 also has the effect of opening further flow ports 54 at the lower end of the member 24, which permit bypass of the ball 46, allowing fluid to circulate through the lower part of the drill string. In use, the casing scraper 10 will typically form part of a drill string, and be located above the drill bit. The drill string is first utilised to carry out a drilling operation where, for example, the cement plug and casing shoe at the bottom of a cemented casing is drilled out, and the bore then extended beyond the end of the existing casing. During the drilling operation the cleaning members 22 remain in the retracted configuration, within the body, and are thus protected from wear and damage. Once the bore has been extended to the required depth the string is pulled out to locate the casing scraper 10 in the end of the casing, where a liner hanger is to be located. The casing scraper is then actuated, by pumping the ball 46 down from surface to engage with the ball catcher 44, such that a significant pressure differential is created across the actuating member 24, sufficient to move the member 24 and extend the cleaning members 22. The pressure drop that occurs when the actuating member 24 moves, due to the opening of the jetting nozzles 48, and the flow ports 54, is detectable at surface and provides an indication to the operators that the scraper 10 has been actuated. The string is then rotated and axially reciprocated, such that the extended cleaning members 22 move across the inner surface of the casing, the flow of fluid from the nozzles 48 removing dislodged debris from the cleaning site and carrying the debris to surface. The compliant mounting of the cleaning member outer portions 30 prevents the cleaning members 22 from jamming in the casing and maintains a degree of pressure on the casing wall.

Following completion of the cleaning operation, the drill string is pulled out of the bore. The cleaning members 22 need not be retracted, as the compliant mounting of the outer portions 30, and the downward inclination of the cleaning blades 32, allows the extended cleaning members 22 to be dragged upwardly through the casing.

. It will be apparent to those of skill in the art that a cleaning apparatus in accordance with embodiments of the present invention offers many advantages over conventional casing scrapers, and allows a cleaning apparatus to be incorporated in a drill string, thus providing a significant saving in time when it is desired to carry out a cleaning operation following a drilling operation.

It will also be apparent to those of skill in the art that the above-described embodiment is merely exemplary of the present invention, and that various modifications and improvements may be made thereto without departing from the scope of the present invention.

Claims

1. Downhole cleaning apparatus comprising: a body; and at least one cleaning member mounted on the body, the cleaning member being selectively movable from a retracted configuration to an extended cleaning configuration.

2. Apparatus as claimed in claim 1, wherein the apparatus is adapted to be mounted on a drill string above a drill bit.

3. The apparatus of claim 1 or 2, wherein the cleaning member comprises inner and outer portions, wherein the initial location of the inner and outer portions is such that there is no cavity between the portions.

4. The apparatus of claim 1, 2 or 3, wherein the cleaning member includes a compliant element.

5. The apparatus of claim 4, wherein an outer portion of the cleaning member is radially compliant.

6. The apparatus of claim 5, wherein the outer portion of the cleaning member is, in the extended configuration, biased radially outwards.

7. The apparatus of claim 6, wherein the outer portion of the cleaning member is mounted on a spring, and, on release, moves radially outwards under the influence of the spring.

8. The apparatus of any of the preceding claims, wherein the cleaning member is configurable to be positively retained in the retracted configuration.

9. The apparatus of any of the preceding claims, wherein an outer portion of the cleaning member is adapted to be initially restrained in the retracted configuration.

10. The apparatus of claim 9, wherein the cleaning member is adapted to be retained by a retaining member extending between the cleaning member and the body.

11. The apparatus of claim 10, wherein the retaining member is a shear member.

12. The apparatus of any of claims 1 to 11, whereby radial extension of the cleaning member is achieved by linear radial translation of the cleaning member.

13. The apparatus of any of claims 1 to 12, wherein the cleaning member positively engages an actuating member.

14. The apparatus of claim 13, wherein the cleaning member and the actuating member engage via a dovetail arrangement.

15. The apparatus of any of the preceding claims, wherein the cleaning member is configured to be actuated by fluid pressure.

16. The apparatus of claim 15, wherein the apparatus is configured such that fluid pressure acts indirectly on the cleaning member via an actuating member.

17. The apparatus of claim 16, wherein the actuating member includes a cam member arranged to produce radial movement of the cleaning member in response to axial movement of the actuating member.

18. The apparatus of claim 16, wherein the cam member positively engages the cleaning member such that the radial movement of the cleaning member is restricted in the absence of axial movement of the cam member.

19. The apparatus of claim 18, wherein the positive engagement between the cam member and the cleaning member is provided by cooperating linearly extending profiles to restrict rotation of the cleaning member relative to the body.

20. The apparatus of any of the preceding claims, comprising an actuating member for actuating the cleaning member, the actuation member being configured to define a flow restriction and create a fluid pressure differential there across.

21. The apparatus of claim 20, wherein the actuating member is configured to engage with a flow restricting member, selectively located in the actuating member.

22. The apparatus of claim 21, wherein the flow-restricting member is adapted to substantially occlude an actuating member through-bore.

23. The apparatus of any of the preceding claims, comprising an actuating member arranged to release an outer portion of the cleaning member relative to an inner portion of the cleaning member.

24. The apparatus of claim 23, wherein the release of the outer portion is achieved by the actuating member moving the outer member radially relative to the inner member and separating a coupling member between the portions.

25. The apparatus of claim 24, wherein the actuating member is biased towards a cleaning member retracting position.

26. The apparatus of claim 25, wherein a spring is located between the actuating member and the body.

27. The apparatus of any of the preceding claims, wherein the body includes at least one flow port that is adapted to be selectively opened to permit flow of fluid directly from the interior of the body to the exterior of the body.

28. The apparatus of claim 27, wherein the port is directed towards the cleaning member.

29. The apparatus of claim 27 or 28, wherein the flow port is adapted to be opened as the cleaning member is extended.

30. The apparatus of any of the preceding claims, wherein the cleaning member is located in a window in the body.

31. The apparatus of claim 30, wherein seals are provided between the cleaning member and the body.

32. The apparatus of any of the preceding claims, wherein the body defines an outer diameter and the retracted cleaning member defines an outer diameter no greater than the body outer diameter.

33. The apparatus of any of the preceding claims, wherein a plurality of circumferentially spaced cleaning members are provided.

34. The apparatus of any of the preceding claims, where the cleaning member includes cleaning blades.

35. The apparatus of claim 34, wherein the blades are inclined.

36. A method of cleaning downhole tubing, the method comprising: mounting a cleaning apparatus on a drill string above a drill bit; and reconfiguring a cleaning member on the cleaning apparatus to a cleaning configuration.

37. The method of claim 36, comprising moving the cleaning member to the cleaning configuration following a drilling operation.

38. The method of claim 36 or 37, comprising cleaning a section of casing wall ready to receive a liner hanger.

39. The method of any of claims 35 to 37, comprising withdrawing the apparatus from a bore with the cleaning member in the cleaning configuration.

40. The method of any of claims 35 to 39, comprising dropping a flow restriction member into the drill string when it is desired to actuate the apparatus.